MCQOPTIONS
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MCQOPTIONS
This section includes 244 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be |
| A. | 00% |
| B. | round 90% |
| C. | nywhere between 75% and 90% |
| D. | ess than 50% |
| Answer» E. | |
| 2. |
Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control |
| A. | rum type controller is used |
| B. | hree point starter is used |
| C. | our point starter is used |
| D. | ll above can be used |
| Answer» B. hree point starter is used | |
| 3. |
If a D.C. motor is to be selected for conveyors, which motor would be preferred ? |
| A. | eries motor |
| B. | hunt motor |
| C. | ifferentially compound motor |
| D. | umulative compound motor |
| Answer» B. hunt motor | |
| 4. |
Which of the following motors one will choose to drive the rotary compressor? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Universal motor |
| D. | Synchronous motor |
| Answer» E. | |
| 5. |
When two D.C. series motors are connected in parallel, the resultant speed is |
| A. | More than the normal speed |
| B. | Loss than the normal speed |
| C. | Normal speed |
| D. | Zero |
| Answer» B. Loss than the normal speed | |
| 6. |
The plugging gives the |
| A. | Zero torque braking |
| B. | Smallest torque braking |
| C. | Highest torque braking |
| D. | None of the above |
| Answer» D. None of the above | |
| 7. |
The speed of a D.C. shunt motor more than its full-load speed can be obtained by |
| A. | Decreasing the field current |
| B. | Increasing the field current |
| C. | Decreasing the armature current |
| D. | Increasing the armature current |
| Answer» B. Increasing the field current | |
| 8. |
The current drawn by the armature of D.C. motor is directly proportional to |
| A. | The torque required |
| B. | The speed of the motor |
| C. | The voltage across the terminals |
| D. | None of the above |
| Answer» B. The speed of the motor | |
| 9. |
Following motor is used where high starting torque and wide speed range control is required. |
| A. | Single phase capacitor start |
| B. | Induction motor |
| C. | Synchronous motor |
| D. | D.C. motor |
| Answer» E. | |
| 10. |
The condition for maximum power in case of D.C. motor is |
| A. | Back e.m.f. = 2 × supply voltage |
| B. | Back e.m.f. = I × supply voltage |
| C. | Supply voltage =I × back e.m.f. |
| D. | Supply voltage = back e.m.f. |
| Answer» C. Supply voltage =I × back e.m.f. | |
| 11. |
D.C. shunt motors are used for driving |
| A. | Trains |
| B. | Cranes |
| C. | Hoists |
| D. | Machine tools |
| Answer» E. | |
| 12. |
Which of the following motors is most suitable for signaling devices and many kinds of timers? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Induction motor |
| D. | Reluctance motor |
| Answer» E. | |
| 13. |
D.C. generators are installed near the load centers to reduce |
| A. | Iron losses |
| B. | Line losses |
| C. | Sparking |
| D. | Corona losses |
| Answer» C. Sparking | |
| 14. |
Why are the D.C. motors preferred for traction applications? |
| A. | Torque and speed are inversely proportional to armature current |
| B. | Torque is proportional to armature current |
| C. | Torque is proportional to square root of armature current |
| D. | The speed is inversely proportional to the torque and the torque is proportional to square of armature current |
| Answer» E. | |
| 15. |
Sparking, is discouraged in a D.C. motor because |
| A. | It increases the input power consumption |
| B. | Commutator gets damaged |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» C. Both (A) and (B) | |
| 16. |
D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the |
| A. | Series motor |
| B. | Shunt motor |
| C. | Compound motor |
| D. | Any of the above |
| Answer» B. Shunt motor | |
| 17. |
The starting resistance of a D.C. motor is generally |
| A. | Low |
| B. | Around 500 Q |
| C. | 1000 Q |
| D. | Infinitely large |
| Answer» B. Around 500 Q | |
| 18. |
Torque developed by a D.C. motor depends upon |
| A. | Magnetic field |
| B. | Active length of the conductor |
| C. | Current flow through the conductors |
| D. | All above factors |
| Answer» E. | |
| 19. |
D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this |
| A. | Series motor |
| B. | Shunt motor |
| C. | Compound motor |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 20. |
The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by |
| A. | Reducing the field current |
| B. | Decreasing the armature current |
| C. | Increasing the armature current |
| D. | Increasing the excitation current |
| Answer» B. Decreasing the armature current | |
| 21. |
Which motor should not be started on no-load? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 22. |
Which D.C. motor has got maximum self relieving property? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 23. |
For which of the following applications a D.C. motor is preferred over an A.C. motor? |
| A. | Low speed operation |
| B. | High speed operation |
| C. | Variable speed operation |
| D. | Fixed speed operation |
| Answer» D. Fixed speed operation | |
| 24. |
Sparking at the commutator of a D.C. motor may result in |
| A. | Damage to commutator segments |
| B. | Damage to commutator insulation |
| C. | Increased power consumption |
| D. | All of the above |
| Answer» E. | |
| 25. |
Which method of braking is generally used in elevators? |
| A. | Plugging |
| B. | Regenerative braking |
| C. | Rheostat braking |
| D. | None of the above |
| Answer» B. Regenerative braking | |
| 26. |
Which of the following motor is preferred for operation in highly explosive atmosphere? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» D. Battery operated motor | |
| 27. |
For a D.C. shunt motor if the excitation is changed |
| A. | Torque will remain constant |
| B. | Torque will change but power will remain constant |
| C. | Torque and power both will change |
| D. | Torque, power and speed, all will change |
| Answer» C. Torque and power both will change | |
| 28. |
If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Differentially compound motor |
| D. | Cumulative compound motor |
| Answer» B. Shunt motor | |
| 29. |
If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking |
| A. | Regenerative |
| B. | Plugging |
| C. | Dynamic braking |
| D. | None of the above |
| Answer» C. Dynamic braking | |
| 30. |
In variable speed motor |
| A. | A stronger commutating field is needed at low speed than at high speed |
| B. | A weaker commutating field is needed at low speed than at high speed |
| C. | Same commutating field is needed at low speed than at high speed |
| D. | None of the above is correct |
| Answer» C. Same commutating field is needed at low speed than at high speed | |
| 31. |
D.C. generators are normally designed for maximum efficiency around |
| A. | Full load |
| B. | Rated r.p.m. |
| C. | Rated voltage |
| D. | All of the above |
| Answer» B. Rated r.p.m. | |
| 32. |
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor |
| A. | Of lower H.P. should be selected |
| B. | Of higher H.P. should be selected |
| C. | Can be used for 50°C ambient temperature also |
| D. | Is to be de-rated by a factor recommended by manufacturer and select the next higher H.P. motor |
| Answer» E. | |
| 33. |
The power mentioned on the name plate of an electric motor indicates |
| A. | The power drawn in kW |
| B. | The power drawn in kVA |
| C. | The gross power |
| D. | The output power available at the shaft |
| Answer» E. | |
| 34. |
No-load speed of which of the following motor will be highest? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differentiate compound motor |
| Answer» C. Cumulative compound motor | |
| 35. |
The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is |
| A. | 2.36% |
| B. | 4.76% |
| C. | 6.77% |
| D. | 8.84% |
| Answer» C. 6.77% | |
| 36. |
In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be |
| A. | Almost negligible |
| B. | Rated full-load current |
| C. | Less than full-load current |
| D. | More than full-load current |
| Answer» E. | |
| 37. |
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit |
| A. | A resistance is connected in series with armature |
| B. | A resistance is connected parallel to the armature |
| C. | Armature is temporarily open circuited |
| D. | A high value resistor is connected across the field winding |
| Answer» B. A resistance is connected parallel to the armature | |
| 38. |
Which of the following loss in a D.C. generator varies significantly with the load current? |
| A. | Field copper loss |
| B. | Windage loss |
| C. | Armature copper loss |
| D. | None of the above |
| Answer» D. None of the above | |
| 39. |
A three point starter is considered suitable for |
| A. | Shunt motors |
| B. | Shunt as well as compound motors |
| C. | Shunt, compound and series motors |
| D. | All D.C. motors |
| Answer» C. Shunt, compound and series motors | |
| 40. |
When the armature of a D.C. motor rotates, e.m.f. induced is |
| A. | Self-induced e.m.f. |
| B. | Mutually induced e.m.f. |
| C. | Back e.m.f. |
| D. | None of the above |
| Answer» D. None of the above | |
| 41. |
Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity? |
| A. | Swinburne's test |
| B. | Hopkinson's test |
| C. | Field test |
| D. | Brake test |
| Answer» D. Brake test | |
| 42. |
Which one of the following is not the function of pole shoes in a D.C. machine? |
| A. | To reduce eddy current loss |
| B. | To support the field coils |
| C. | To spread out flux for better uniformity |
| D. | To reduce the reluctance of the magnetic path |
| Answer» B. To support the field coils | |
| 43. |
In D.C. shunt motors as load is reduced |
| A. | The speed will increase abruptly |
| B. | The speed will increase in proportion to reduction in load |
| C. | The speed will remain almost/constant |
| D. | The speed will reduce |
| Answer» D. The speed will reduce | |
| 44. |
These days D.C. motors are widely used in |
| A. | Pumping sets |
| B. | Air compressors |
| C. | Electric traction |
| D. | Machine shops |
| Answer» D. Machine shops | |
| 45. |
Three point starter can be used for |
| A. | Series motor only |
| B. | Shunt motor only |
| C. | Compound motor only |
| D. | Both shunt and compound motor |
| Answer» E. | |
| 46. |
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors? |
| A. | Low cost |
| B. | Wide speed range |
| C. | Stability |
| D. | High starting torque |
| Answer» B. Wide speed range | |
| 47. |
For starting a D.C. motor a starter is required because |
| A. | It limits the speed of the motor |
| B. | It limits the starting current to a safe value |
| C. | It starts the motor |
| D. | None of the above |
| Answer» C. It starts the motor | |
| 48. |
The ratio of starting torque to full-load torque is least in case of |
| A. | Series motors |
| B. | Shunt motors |
| C. | Compound motors |
| D. | None of the above |
| Answer» C. Compound motors | |
| 49. |
A direct on line starter is used: for starting motors |
| A. | Up to 5 H.P. |
| B. | Up to 10 H.P. |
| C. | Up to 15 H.P. |
| D. | Up to 20 H.P. |
| Answer» B. Up to 10 H.P. | |
| 50. |
The main disadvantage of the Ward-Leonard control method is |
| A. | High initial cost |
| B. | High maintenance cost |
| C. | Low efficiency at high loads |
| D. | All of the above |
| Answer» E. | |